Wenjing Zhang

Hypoglycemic property of acidic polysaccharide extracted from Saccharina japonica and its potential mechanism

In the present study, a sulfated polysaccharide fucoidan extracted from Saccharina japonica was administered to normal and alloxan-diabetic rats/mice, and its effects on glycemia, insulin and serum lipid levels were evaluated. Fucoidan administered at 200 or 1200 mg/kg body weight/day could significantly reduce the blood glucose level by 22% and 34%, respectively, in alloxan-induced diabetic rats. Serum insulin levels in diabetic mice were increased by the administration of fucoidan (P<0.05). The results of an oral glucose tolerance test (OGTT) revealed that fucoidan treatment had some effect on glucose disposal after 15 days of treatment. Furthermore, fucoidan altered plasma lipid levels by lowering cholesterol, triglyceride and plasma low-density lipoprotein concentrations, while elevating plasma high-density lipoprotein cholesterol at 100 or 300 mg/kg body weight/day. The results suggested that fucoidan exhibited a considerable hypoglycemic effect, possibly by stimulating pancreatic release of insulin and/or by reducing insulin metabolism. Our results indicated that fucoidan could be developed as a potential oral hypoglycemic agents or functional food for the management of diabetes.

A comparative study of the anticoagulant activities of eleven fucoidans.

Seven fucoidans that differed only with respect to the average molecular weight and four fucoidans that differed with respect to both the molar ratio of fucose to galactose and the average molecular weight were obtained. The anticoagulant activities of these fucoidans were determined in order to understand the effects of the average molecular weight and the content of galactose. Fucoidans Y5-Y11, with the average molecular weight in the range of 50.1-8.4 kDa, showed decreasing activity at three concentrations and dose-dependent activity in the APTT and TT assays. Y1-Y4, which differed with respect to the average molecular weight and the molar ratio of fucose to galactose, exhibited complicated results in the APTT and TT assays. It was shown that not only the average molecular weight but also the molar ratio of fucose to galactose affected the anticoagulant activity of fucoidans.

Characterization of laminaran and a highly sulfated polysaccharide from Sargassum fusiforme

The crude polysaccharide (HFS) from Sargassum fusiforme (Hizikia fusiforme) was extracted using 0.1M HCl and was fractionated by anion-exchange chromatography into three fractions: HFS-1, HFS-2, and HFS-3. Based on the chemical analysis, HFS-1 was composed of laminaran, HFS-2 was a mixture of alginate and sulfated heteropolysaccharides, and HFS-3 was primarily composed of sulfated galactofucan. The NMR spectra revealed that HFS-1 was composed of a soluble laminaran with chains that are terminated by β-d-glucose residues. In contrast, the spectra obtained for HFS-2 were still complex, even after most of the alginate was removed. In addition, HFS-3 might contain 3-linked fucan sulfated at C-2, 6-linked galactan sulfated at C-2 and branched at C-4 by 2-sulfated Fuc, and galactofucan with a backbone of either alternating Gal and Fuc sulfated at C-2 or alternating (Gal)n and (Fuc)n sulfated at C-2. Moreover, HFS-3 also contained small amounts of fucoglucuronomannan and xylan.

The antioxidant activities and neuroprotective effect of polysaccharides from the starfish Asterias rollestoni

After the starfish was defatted with isopropyl alcohol and ethanol, crude polysaccharide was extracted by 0.15 mol/L HCl. Anion exchange chromatography was performed to fractionate the sample into two fractions, SF-1 and SF-2. Chemical analysis showed that the major component of SF-1 was a glucan consisting of a backbone of 1→3 linked β-D-glucopyranose residues, and it had a minor glucan component containing a backbone of 1→3 linked α-D-glucopyranose residues. SF-2 was a mannoglucan sulfate. SF-2 displayed the highest antioxidant activity among the polysaccharides. Moreover, SF-1 and SF-2 exhibited neuroprotective activities in a neurotoxicity model of Parkinsons disease (PD).

A study of neuroprotective and antioxidant activities of heteropolysaccharides from six Sargassum species.

Heteropolysaccharides were extracted from Sargassum integerrimum (S.I), Sargassum maclurei (S.M), Sargassum naozhouense (S.N), Spiraea thunbergii (S.T), Sargassum hemiphyllum (S.H) and Sargassum fusiforme (S.F), and their neuroprotective effects and antioxidant activities were investigated. It showed that S.I, S.N, S.T and S.F exhibited neuroprotective activities, whereas S.H and S.M did not. For this reason, they were separated by anion-exchange chromatography. It was apparent that the fraction 2 represented the principal difference between the active and non-active compounds. However, it did not correlate with neuroprotective effect. In addition, the results on antioxidant activities showed that the hydroxyl-radical scavenging effect contribute to the neuroprotective effect of S.T and S.N, and the DPPH-radical scavenging effect and reducing power contribute to S.T, S.F and S.I. However, the superoxide-radical scavenging effect did not correlate with neuroprotective activity. The conclusion was that the neuroprotective activity of the family of compounds investigated depended on a variety of factors.

Structural analysis of heteropolysaccharide from Saccharina japonica and its derived oligosaccharides.

Degraded fucoidan (F1) was desulfated by DMSO-MeOH. And anion exchange chromatography was performed to fractionate desulfated F1 (ds-F1) into five fractions. Electrospray ionization mass spectrometry (ESI-MS) showed that each fraction contained at least one set of neutral and/or sulfated fucooligosaccharides in the form of methyl glycosides. And the structures of oligomeric fragments were characterized by ESI-CID-MS/MS and ESI-CID-MS/MS/MS. In addition, more structural features were shown by NMR. Therefore, it was concluded that LF1 contained a backbone of (1→3)-linked fucopyranose residues sulfated at C-4 and branched at C-2 by fucopyranose residues and fucoglucuronomannan, fucoglucuronan, galactan and xylan were found in LF-5. Finally, it was concluded that F1 was the middle component, which contained the information of both F0.5 and F2, indicating that the differences between F1 and F0.5, F2 might be derived primarily from the different needs of algae itself.

The Structure-Activity Relationship between Marine Algae Polysaccharides and Anti-Complement Activity

In this study, 33 different polysaccharides were prepared to investigate the structure-activity relationships between the polysaccharides, mainly from marine algae, and anti-complement activity in the classical pathway. Factors considered included extraction methods, fractionations, molecular weight, molar ratio of galactose to fucose, sulfate, uronic acid (UA) content, linkage, branching, and the type of monosaccharide. It was shown that the larger the molecular weights, the better the activities. The molar ratio of galactose (Gal) to fucose (Fuc) was a positive factor at a concentration lower than 10 µg/mL, while it had no effect at a concentration more than 10 µg/mL. In addition, sulfate was necessary; however, the sulfate content, the sulfate pattern, linkage and branching had no effect at a concentration of more than 10 µg/mL. Moreover, the type of monosaccharide had no effect. Laminaran and UA fractions had no activity; however, they could reduce the activity by decreasing the effective concentration of the active composition when they were mixed with the active compositions. The effect of the extraction methods could not be determined. Finally, it was observed that sulfated galactofucan showed good anti-complement activity after separation.

The neuroprotective activities and antioxidant activities of the polysaccharides from Saccharina japonica.

The crude polysaccharide (W) was extracted by water from Saccharina japonica and five fractions were separated by anion-exchange chromatography. And their chemical constituents, neuroprotective activities and antioxidant activities were studied. It showed that W had the neuroprotective activity while its fractions did not. In addition, the fractions displayed higher activities on hydroxyl-radical scavenging effects and reducing power than these of W. Moreover, it was speculated that the neuroprotective activities of samples were related to the hydroxyl-radical scavenging effect and reducing power while did not relate to superoxide-radical scavenging effect. Finally, it was concluded that some fractions could be good candidate antioxidants in food chemistry owing to the high antioxidant activities and their non-toxic characteristics.

The neuroprotective activities of heteropolysaccharides extracted from Saccharina japonica

Crude fucoidan extracted from Saccharina japonica was separated by anion-exchange chromatography. Then, the neuroprotective activities of the crude fucoidan (J) and its fractions (J0.4, J0.5, J1 and J2) were tested. J, J0.4 and J0.5 were shown to have neuroprotective effects. To simplify the structural features of the compounds, crude fucoidan was degraded to obtain low molecular weight fucoidan (DJ). DJ was further fractionated into DJ0.5, DJ1 and DJ2, and the neuroprotective activities of these fractions were determined. This analysis revealed that DJ and DJ0.5 retained the neuroprotective activity. However, the DJ0.5 fraction remained very complex. Thus, DJ0.5 was further separated into six fractions (F0.1, F0.2, F0.3, F0.4, F0.5 and F1). Finally, it was concluded that the anion-exchange fractions F0.1, F0.2 and F0.3 exhibited neuroprotective activities. These results suggest that heteropolysaccharides might contribute to the neuroprotective activity. Moreover, the neuroprotective heteropolysaccharide fractions contained relatively low fucose (less than 20%) and sulfate (25%), high UA content (more than 10%) and a high molar ratio of all other monosaccharides.

Structural analysis of sulfated fucan from Saccharina japonica by electrospray ionization tandem mass spectrometry

Desulfation of a fucoidan from Saccharina japonica by treatment with DMSO-MeOH resulted in partial degradation of polymeric molecules by methanolysis giving rise to a mixture of neutral, monosulfated, and disulfated fucooligosaccharides in the form of methyl glycosides. These oligomeric fragments were characterized by ESI-MS and ESI-CID-MS/MS. It was found that oligosaccharide structures coincided with the polysaccharide backbone built up mainly of (1→3)-linked fucose residues sulfated at positions 4 and 2.